Certain materials, when exposed to ionizing radiation, can be stimulated to emit a measurable signal that may be used to estimate the received radiation dose. Certain of these materials may be incorporated into a dosimeter that is worn or carried by an individual to measure the individual's exposure. A thermoluminescent dosimeter (TLD) is an example. To be effective in monitoring radiation exposure, the TLD must be worn or carried by the individual during periods of possible radiation exposure. For medical/industrial applications of ionizing radiation, dosimeters are used to assess the quality of the treatment or process.
Dosimetry systems and techniques exist that exploit radiation-induced signals emanating from biological materials. In some of these techniques, the signals may be measured in vivo. Examples of such techniques include electron paramagnetic resonance (EPR) dosimetry, which may be used to measure signals in teeth, fingernails, toenails, bone and hair. These techniques hold out the promise for screening (i.e., as part of a triage effort), at a point-of-care facility, large populations groups that may have been exposed to ionizing radiation.
EPR dosimetry is based on the following: (1) ionizing radiation generates unpaired electrons (e.g., free radicals) in proportion to the absorbed dose; (2) EPR dosimetry can selectively and sensitively detect and determine the number of unpaired electrons; and (3) the unpaired electrons can persist in some tissues, such as teeth and nails, with enough stability so as to be measured by EPR dosimetry weeks to years after radiation exposure.